溴酚红光度法测定微量阳离子表面活性剂

Determination of Cationic Surfactants with Bromphenol Red by Spectrophotometry

在聚乙烯醇存在的 pH值为 5.5左右的溶液中 ,溴酚红与阳离子表面活性剂形成离子缔合物 ,溶液由红棕色变为蓝紫色 ,可以用于水相直接测定阳离子表面活性剂 .最大吸收波长 590nm ,摩尔吸光系数分别为 3.9× 10 3L·mol- 1·cm- 1(溴化十六烷基三甲基铵 )、4 .0× 10 3L·mol·cm- 1(溴化十六烷基吡啶 ) ,方法简便、快速 ,用于合成水样中微量阳离子表面活性剂测定 ,结果满意 .

A spectrophotometric method has been developed for the determination of cationic surfactants based on the formation of ion-associate compounds of bromphenol red with cationic surfactants in aqueous solution in the presence of polyvinyl alcohol.The desirable acidity ranges from pH5.09 to pH5.72.The maximum absorption exhibits at 590nm and the molar absorptivities are 3.9×10 3L·mol -1 ·cm -1 for CTAB and 4.0×10 3L·mol -1 ·cm -1 for CPB.The result indicated that the colour reaction can be applied to direct spectrophotometric determination of cationic surfactants in aqueous solution.